Radon is a gaseous, radioactive element occurring naturally in nearly all soils. Created by the natural decay of uranium, radon ordinarily escapes from the ground and evaporates harmlessly into the atmosphere. Problems arise, however, when a building, especially a residential building such as a house, impedes the release of radon from the ground into the atmosphere. Radon can enter the building through open sump pits, cracks and other holes in the foundation, and cavities inside foundation walls, such as in a basement wall having concrete block construction. A building can trap radon inside, where it can build up. High concentrations of radon are widely believed to contribute to lung cancer, particularly among cigarette smokers.
When testing of a building reveals a high concentration of radon, radon mitigation is recommended. There are several radon mitigation techniques known in the art that reduce the amount of radon that enters a building. The most basic technique comprises sealing cracks and other openings in the building""s foundation. Sealing rarely is effective by itself, however. Those of skill in the art will appreciate that it is difficult to identify and permanently seal all places where radon may enter a building. In addition, normal settling of a building often opens new radon entry routes, and may reopen old ones.
Typically, sealing is accompanied by a technique known as xe2x80x9cactive depressurization.xe2x80x9d In a radon mitigation system employing active depressurization, a network of pipes is installed in or around the building. At least one open end of the network of pipes is placed in proximity to the radon emerging from the ground. An exhaust fan connected to the network of pipes creates a vacuum that draws radon-laced air into the pipe and expels it outside the building at a safe level above ground.
Different types of active depressurization are appropriate for different building foundations. If the building has a concrete slab foundation, or is over a basement with a concrete slab floor, the radon mitigation system usually comprises one of four types of active depressurization: subslab depressurization, drain tile depressurization, sump pit depressurization, or block wall depressurization. These techniques are not mutually exclusive. All, or any combination, of these techniques may be used in a given radon mitigation system.
Subslab depressurization is the most common radon mitigation technique. Depressurization pipes are inserted through the concrete slab into the crushed rock or soil underneath. Alternatively, depressurization pipes may be inserted below the concrete slab from outside the building. A fan connected to the pipes draws the radon gas from below the concrete slab and then releases it into the atmosphere.
If the building has drain tiles to direct water away from the foundation of the building, and if the drain tiles form a complete loop around the foundation, depressurization of these drain tiles also may be effective in reducing radon levels. Depressurization pipes are inserted into the drain tile loop. A fan connected to the pipes draws the radon gas from the drain tile loop and then releases it into the atmosphere.
If the building has sump pit containing a sump pump to remove unwanted water, the sump pit can be capped so that it can continue to drain water but also serve as depressurization point. A depressurization pipe is inserted into through the sump pit cap, and then a fan connected to the pipe draws the radon gas from the sump pit and then releases it into the atmosphere.
If the building""s basement comprises a hollow concrete block foundation walls, the hollow spaces within the concrete block wall may be depressurized using a variation of the same technique.
If the building has a crawlspace with an earth or gravel floor, the radon mitigation system usually comprises a technique known as sub-membrane depressurization. According to this technique, the floor of the crawlspace is covered with a heavy plastic sheet. A depressurization pipe is inserted under the plastic sheet and then a fan connected to the pipe draws the radon gas from under the sheet and then releases it into the atmosphere.
Common to each of these radon mitigation systems using active depressurization techniques, is the use of a fan and a network of pipes to draw radon-laced air from the soil and exhaust it to the atmosphere at a safe level above ground. Frequently, the fan is installed in a weatherproof housing located outside the building and slightly above ground level. This location reduces noise load the fan might add if installed inside the building, and permits easy access to the fan for maintenance. The depressurization pipes mate with one side of the fan housing, and an exhaust pipe extends from the opposite side of the fan housing to a predetermined level above ground.
The radon-laced air drawn into a radon mitigation system comprising active depressurization, such as those described herein, normally is about 55xc2x0 F. year-round, and often comprises a high relative humidity. A problem arises when this warm, moist air reaches the exhaust pipe. In colder climates, the air in the exhaust pipe may be chilled below its dew point, causing the moisture in the air to condense on the inner surface of the exhaust pipe. In some circumstances, the quantity of the condensate formed within the exhaust pipe is such that the condensate drains down the inner surface of the exhaust pipe and into the fan housing, potentially damaging the exhaust fan and/or the exhaust fan motor. The owner then is faced with an unexpected, expensive repair. Therefore, it is desired to provide an apparatus for diverting the condensate that forms inside the exhaust pipe in a radon mitigation system away from the exhaust fan, thereby increasing the useful life of the exhaust fan. The desired apparatus will be easily installed, economic to manufacture, reasonably priced, and reliably constructed of readily available materials so that it will withstand exposure to the outdoor elements over many years of use.
The present invention comprises an exhaust system for removing a radon from habitable areas of a building, including an apparatus for diverting condensate which forms within the system away from the exhaust fan, thereby avoiding damage to the exhaust fan and/or the exhaust fan motor and increasing the useful life of the exhaust fan and the exhaust fan motor.
The exhaust system of the present invention comprises an exhaust fan apparatus comprising having an exhaust port and a suction port and enclosing a fan. The operation of the fan draws a radon into the suction port and expels radon from the exhaust port.
One end of a hollow suction conduit is coupled to the suction port. The hollow suction conduit has an inner surface. At least one other end of the hollow suction conduit is located proximate to the radon gas, such as under the concrete slab or basement floor, within the drain tile loop, inside a sump pit, inside the cavities within a concrete block wall, or under s plastic membrane in a crawl space. The hollow suction conduit is otherwise substantially airtight. The operation of the fan draws radon gas into the end(s) of the hollow suction conduit located proximate to the radon gas, and causes the radon gas to be conducted through the hollow suction conduit to the suction port. The suction conduit may comprise a first hollow flexible coupling having an inner surface, a first open end, and a second open end. The first open end of the first hollow flexible coupling is coupled to the suction port, and the second open end is coupled to the suction conduit.
One end of a hollow exhaust conduit is coupled to the exhaust port. The hollow exhaust conduit has an inner surface. At least one other end of the hollow exhaust conduit is located at a predetermined level above ground level. The hollow exhaust conduit is otherwise substantially airtight. The operation of the fan expels radon gas from the exhaust port into the hollow exhaust conduit, and causes the radon gas to be conducted through the hollow exhaust conduit until it is expelled into the atmosphere. The exhaust conduit may comprise a second hollow flexible coupling having an inner surface, a first open end, a second open end. The first open end is coupled to the exhaust conduit, and the second open end is coupled to the exhaust port.
A hollow condensate trap is located within the exhaust conduit. The hollow condensate trap comprises a first open end and a second open end and a hollow interior communicating between the first open end and the second open end. The diameter of the first open end is less than the diameter of the second open end thereby resulting in a conically-shaped sloping outer surface to the condensate trap. The diameter of the second end of the condensate trap is dimensioned to fit within the exhaust conduit. The condensate trap is arranged within the exhaust conduit in a manner that precludes passage of the radon gas between the second open end of the condensate trap and the inner surface of the exhaust conduit. The axis of the condensate trap is substantially coincident with the axis of the exhaust conduit. Thus, a gutter is formed within the exhaust conduit. The gutter comprises the inner surface of the exhaust conduit and the sloping outer surface of the condensate trap. The gutter is positioned to collect condensate which may drain within the exhaust conduit.
A hollow bypass tube having a first open end and a second open end communicates between the exhaust conduit and the suction conduit in a manner bypassing the exhaust fan apparatus. The first open end of the bypass tube communicates through the exhaust conduit to the hollow interior thereof immediately adjacent to the conical surface of the condensate trap and within the gutter, and the second open end of the bypass tube communicates through the suction conduit to the hollow interior thereof. Thus, condensate collected in the gutter is conducting through the bypass tube into the suction conduit.
The hollow bypass tube may be installed by the use of a first and a second hollow bypass tube fitting. Each bypass tube fitting has a first open end and a second open end and a hollow interior communicating between the first open end and the second open end. The first open end of the first bypass tube fitting comprises an annular flange perpendicular to the axial direction of the bypass tube fitting. A surface of the annular flange of the first bypass tube fitting is engaged against the inner surface of the exhaust conduit, and a portion of the first bypass tube fitting is passed through a hole in a wall of the exhaust conduit, so that the second open end of the first bypass tube fitting ends up outside the exhaust conduit. The first open end of the first bypass tube fitting thus is positioned within the exhaust conduit to receive condensate from the gutter. Alternatively, the first open end of the first bypass tube fitting comprises external threads. The first open end of the first bypass tube fitting is threadably engaged with a hole in a wall of the exhaust conduit, so that the second open end of the first bypass tube fitting ends up outside the exhaust conduit.
The first open end of the second bypass tube fitting comprises external threads. The first open end of the second bypass tube fitting is threadably engaged with a hole in a wall of the suction conduit, so that the second open end of the second bypass tube fitting ends up outside the suction conduit. The first open end of the second bypass tube fitting thus is positioned within the suction conduit to deliver condensate to the suction conduit.
After the first and the second bypass tube fittings are positioned, the first open end of the bypass tube is coupled to the second open end of the first bypass tube fitting and the second open end of the bypass tube is coupled to the second open end of the second bypass tube fitting in a manner bypassing the exhaust fan. The condensate received from the gutter by the first open end of the first bypass tube fitting is conducting through the first bypass tube fitting and delivered from the second open end of the first bypass tube fitting into the bypass tube, then conducted through the bypass tube and delivered into the second open end of the second bypass tube fitting, then conducted through the second bypass tube fitting and delivered through the first open end of the second bypass tube fitting into the suction conduit.